Battery cell thermal runaway barrier

ABSTRACT

A thermal runaway barrier for at least significantly slowing down a thermal runaway event within a battery assembly. The thermal runaway barrier includes a layer of a nonwoven fibrous thermal insulation comprising a fiber matrix of inorganic fibers, thermally insulative inorganic particles of irreversibly or permanently expanded expandable inorganic material dispersed within the fiber matrix, and a binder dispersed within the fiber matrix so as to hold together the fiber matrix. An optional organic encapsulation layer may also be used to encapsulate the nonwoven fibrous thermal insulation.

The present invention relates to a barrier for at least significantlyslowing down a thermal runaway event within a battery assembly, e.g.,like a battery assembly used in an electric vehicle.

BACKGROUND

Electric motors used in electric or hybrid vehicles (e.g., automobiles)are powered, at least in part, by batteries. Lithium ion batteries aretypically used in such applications, and they are available in threeforms: prismatic cells, pouch cells or cylindrical-shaped cells. Thesebatteries are disposed within the vehicle compactly to save space.Sometimes one or more of the battery cells or battery modules experiencea thermal runaway event, which can result in many if not all of thebattery cells or battery modules overheating and being destroyed. Thereis a desire in the industry to prevent, stop or at least significantlyslowing down such a thermal runaway event. The present invention is acontribution to that effort.

The background description provided here is for the purpose of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent it is described in this background section, aswell as aspects of the description that may not otherwise qualify asprior art at the time of filing, are neither expressly nor impliedlyadmitted as prior art against the present disclosure.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a thermal runaway barrier isprovided that comprises a layer of a nonwoven fibrous thermal insulationcomprising a fiber matrix of inorganic fibers, thermally insulativeinorganic particles of irreversibly or permanently expanded expandableinorganic material dispersed within the fiber matrix, and a binderdispersed within the fiber matrix so as to hold together the fibermatrix. An optional organic encapsulation layer may also be included forenclosing the layer of nonwoven fibrous thermal insulation. An optionalinorganic encapsulation layer may also be included for enclosing thelayer of nonwoven fibrous thermal insulation.

In another aspect of the present invention, a battery cell module orassembly for an electric vehicle is provided. The battery cell module orassembly comprises a plurality of battery cells disposed in a housing,and a plurality of thermal runaway barriers according to the presentinvention. The battery cells are lined up in a row or stack, with onethermal runaway barrier being disposed between each pair of adjacentbattery cells, or between a predetermined number of battery cells (e.g.,after every third battery cell), or between battery modules.

In a further aspect of the present invention, a method is provided formaking a thermal runaway barrier according to the present invention,where the method comprises forming the layer of nonwoven fibrous thermalinsulation using a wet-laid process or dry-laid process.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

Descriptions corresponding to the included figures can be within thisdescription.

FIG. 1 is a schematic end view of a fiber matrix layer and an optionalencapsulation layer that may be used in a thermal runaway barrierapplication.

FIG. 2 is a schematic side view of a battery module of battery cells,with thermal runaway barriers disposed between adjacent battery cells.

FIG. 3 is a schematic top view of a battery pack of battery modules,with thermal runaway barriers placed between adjacent battery modulesand/or on the top of the battery modules.

FIG. 4 is a photographic perspective view of a thermal runaway barrierencapsulated with an adhesive-backed organic polymeric layer withrelease liners and an expanding gas outlet/notch.

FIG. 5 is a schematic side view of a Dry-laid process for manufacturinga battery cell thermal runaway barrier, according to one embodiment ofthe present invention.

FIG. 6 is a cross-sectional view of one embodiment of a thermal runawaybarrier showing multiple expanding gas vent holes formed through theencapsulating film, according to one embodiment of the invention.

FIG. 7 is a cross-sectional view of another embodiment of a thermalrunaway barrier showing multiple expanding gas vent holes in the form ofnotches formed through the encapsulating film, according to anotherembodiment of the invention.

FIG. 8 is a top plan view of an additional embodiment of a thermalrunaway barrier with two different types of expanding gas vent holesformed through the encapsulation film.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

In describing preferred embodiments of the invention, specificterminology is used for the sake of clarity. The invention, however, isnot intended to be limited to the specific terms so selected, and eachterm so selected includes all technical equivalents that operatesimilarly.

As used herein, the terms “preferred” and “preferably” refer toembodiments described herein that can afford certain benefits, undercertain circumstances. However, other embodiments may also be preferred,under the same or other circumstances. Furthermore, the recitation ofone or more preferred embodiments does not imply that other embodimentsare not useful and is not intended to exclude other embodiments from thescope of the invention.

As used herein and in the appended claims, the singular forms “a,” “an,”and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a” or “the” component mayinclude one or more of the components and equivalents thereof known tothose skilled in the art. Further, the term “and/or” means one or allthe listed elements or a combination of any two or more of the listedelements.

It is noted that the term “comprises” and variations thereof do not havea limiting meaning where these terms appear in the accompanyingdescription. Moreover, “a,” “an,” “the,” “at least one,” and “one ormore” are used interchangeably herein. Relative terms such as left,right, forward, rearward, top, bottom, side, upper, lower, horizontal,vertical, and the like may be used herein and, if so, are from theperspective observed in the drawing. These terms are used only tosimplify the description, however, and not to limit the scope of theinvention in any way.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention. Whereapplicable, trade designations are set out in all uppercase letters.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements (e.g., preventingand/or treating an affliction means preventing, treating, or bothtreating and preventing further afflictions).

As used herein, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

“Ambient conditions” means at 25° C. and 101.3 kPa pressure.

“Average” means number average, unless otherwise specified.

“Continuous” means extending across a single, unified area along a givenlayer (a perforated sheet can be continuous);

“Cure” refers to exposing to radiation in any form, heating, or allowingto undergo a physical or chemical reaction that results in hardening oran increase in viscosity.

“Discontinuous” means extending across a plurality of discrete areasalong a given layer, where the discrete areas are spaced apart from eachother;

“Size” refers to the longest dimension of a given object or surface.

“Substantially” means to a significant degree, as in an amount of atleast 50%, 60, 70, 80, 90, 95, 96, 97, 98, 99, 99.5, 99.9, 99.99, or99.999%, or 100%.

“Thickness” means the distance between opposing sides of a layer ormultilayered article.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range in increments commensurate with the degree ofaccuracy indicated by the end points of the specified range (e.g., for arange of from 1.000 to 5.000, the increments will be 0.001, and therange will include 1.000, 1.001, 1.002, etc., 1.100, 1.101, 1.102, etc.,2.000, 2.001, 2.002, etc., 2.100, 2.101, 2.102, etc., 3.000, 3.001,3.002, etc., 3.100, 3.101, 3.102, etc., 4.000, 4.001, 4.002, etc.,4.100, 4.101, 4.102, etc., 5.000, 5.001, 5.002, etc. up to 5.999) andany range within that range, unless expressly indicated otherwise.

The term “polymer” will be understood to include polymers, copolymers(e.g., polymers formed using two or more different monomers), oligomersand combinations thereof, as well as polymers, oligomers, or copolymersthat can be formed in a miscible blend.

The following Examples have been selected merely to further illustratefeatures, advantages, and other details of the invention. It is to beexpressly understood, however, that while the Examples serve thispurpose, the particular ingredients and amounts used as well as otherconditions and details are not to be construed in a manner that wouldunduly limit the scope of this invention.

Referring to FIG. 1 , a fiber matrix layer 10 useful in a thermalrunaway barrier application contains nonwoven inorganic (i.e.,nonmetallic) or otherwise heat resistant fibrous insulation material,thermally insulative ceramic or otherwise nonmetallic inorganicparticles, and an organic or inorganic binder. As used herein,nonmetallic means it is not a metal or metal alloy. Optionally, thefiber matrix layer 10 is encapsulated with an organic polymeric layer12.

Referring to FIG. 2 , an exemplary battery module 20 includes anassembly of battery cells 22 and a plurality of thermal runaway barriers24. Each thermal runaway barrier 24 can be in the form of one or morefiber matrix layers 10, with or without an encapsulation 12, and thatcan be made from the exemplary materials described herein. A thermalrunaway barrier 24 can be disposed between adjacent battery cells 22,between groups of cells 22, or both, at one or more locations throughoutthe battery module 20. Typically, the battery module 20 rests above acooling plate 26 and a tray 28.

Referring to FIG. 3 , an exemplary battery pack 30 includes a pluralityof battery modules 20, which may each have its own cooling plate 26 andtray 28 or all of the modules 20 may share the same cooling plate 26 andtray 28. A thermal runaway barrier 24, formed from the exemplarymaterials described herein, can be disposed between one or more or alladjacent battery modules 20, on the top of one or more or all of thebattery modules 20 (see reference number 24′), or any combination ofboth. A single or multiple thermal runaway barriers 24 may also bedimensioned so as to cover the tops of all of the battery modules 20.

Referring to FIG. 4 , an exemplary thermal runaway barrier 24 includesone or more fiber matrix layers (not shown) encapsulated with an organicpolymeric layer 12 that covers both sides and the peripheral edge of theone or more fiber matrix layers. In one embodiment, the major oppositefaces of the encapsulating layer 12 are coated with an adhesive (e.g., apressure sensitive adhesive) protected by corresponding release liners14 and 16. It is preferable for the encapsulating layer 12 to includeone or more outlets or openings 18 (e.g., in the form of a notch) thatallows air (e.g., hot air) or other gases to escape from inside theencapsulation 12, rather than cause the encapsulation 12 to swell andexpand like a balloon, e.g., when the air trapped in the encapsulation12 is heated to an elevated temperature (e.g., when the temperature ofone or more of the adjacent battery cells 20 increases).

Referring to FIG. 5 , a conventional dry-laid manufacturing equipmentand processes can be used to manufacture thermal runaway barriers 20according to the invention. Examples of such equipment and processes canbe found described in U.S. Pat. Nos. 9,580,848 (Henderson et al.),9,475,034 (Vincent et al.), 7,491,354 (Anderson), and 6,808,664 (Falk etal.). Such equipment can include a chamber or forming box 40 withmultiple feeder inlets, including an inlet 42 for feeding any desiredcombination of fibers, binder and particles into the box 40, andmultiple inlets 44, 44′ and 44″ for feeding any desired number or typeof filler materials into the box 40. After the fibers are combined andmixed together with the other ingredients, the resulting nonwovenfibrous material 45 is deposited onto a belt 46 that conveys thematerial 45 into, through and out of a baking oven 47 where the binderis cured at least so that the fibrous material 45 can be furtherprocessed. The resulting cured nonwoven fibrous material 45′ is thendie-cut, laser-cut, water-jet cut, or otherwise processed intoindividual nonwoven fiber layers 10 (not shown), which are thenprocessed at an encapsulation station 48, e.g., by having a polymericfilm 12 (not shown) laminated to opposite sides of a single layer 10 ora stack of two or more layers 10. An optional hot melt adhesive orpressure sensitive adhesive can be applied to one or both sides of theencapsulate 12 at corresponding spray stations 49 and 49′. A protectiverelease liner (not shown) can be subsequently applied to each adhesivesurface.

Referring to FIG. 6 , one embodiment of a thermal runaway barrier 24according to the invention includes one or more vent holes 52 formedthrough one or both layers of the encapsulating film 12. The vent holes52 can have any desired shape (e.g., circular, rectangular, oval, etc.),and preferably the vent holes 52 are formed through a portion of thefilm 12 located beyond the periphery of the encapsulated fibrouslayer(s) 10 and still within the periphery of the encapsulation 12,while also providing a path for expanding gases (e.g., air) to escapeout of the space containing the fibrous layer(s) 10. The number, sizeand location of these vent holes 52 can vary as desired.

Referring to FIG. 7 , another embodiment of a thermal runaway barrier 24according to the invention includes two vent holes 54, each in the formof a notch formed through the encapsulating film 12. The vent holes 54can have any desired shape (e.g., semicircular, rectangular, semioval,etc.), and preferably the notches 54 are formed through a portion of thefilm 12 located beyond the periphery of the encapsulated fibrouslayer(s) 10 and past the periphery of the encapsulation 12, while alsoproviding a path for expanding gases (e.g., air) to escape out of thespace containing the fibrous layer(s) 10. The number, size and locationof these notches 54 can vary as desired.

Referring to FIG. 8 , an additional embodiment of a thermal runawaybarrier 24 according to the invention includes two different types ofvent holes 52 and 54 formed through the encapsulation 12, like thosedescribed above relative to FIGS. 6 and 7 .

TABLE 1 Test Materials Material Description Source AG Silica aerogelwith a particle size of 100-700 micrometer and a pore size of 20nanometers available under the designation ENOVA Aerogel IC3110 CabotCorp, Boston, MA, United States EAF68 Aqueous polymer dispersed pressuresensitive adhesive available under the designation VINNAPAS EAF 68 VinylAcetate Ethylene Wacker Chemie AG, Miinchen, Germany EVERM Expandedvermiculite Sun Gro, Agawam, MA, United States EXP Sodium silicateintumescent powder available under the trade designation “EXPANTROL” 3MCompany, St. Paul, MN, United States EXPERL Expanded perlite availableunder the designation EUROCELL 300 Europerl, Pölten, Austria FB Acrylicwater-based spray adhesive available under the trade designation“FASTBOND” 4224 NF 3M Company FS Fumed silica with an average particlesize of 0.2 – 0.3 micrometers available under the trade designationCAB-O-SIL H-5 Cabot Corp, Boston, MA, United States H2345 Hot meltpressure sensitive adhesive available under the designation THERMOGRIPH2345-E71 Bostik, Inc, Milwaukee, WI. United States K1Soda-lime-borosilicate hollow glass microspheres with a density of 0.125g/cc and a median particle size of 65 micrometer available under thedesignation Glass Bubbles K1 3M Company LDM Alkaline earth silicatefiber with a mean fiber diameter of 3.0-3.5 micrometer available underthe designation SAFFIL LDM Unifrax, Tonawanda, NY, United States PACopolyamide powder adhesive with a granular size of 100-500 micrometeravailable under the designation 5350 Shaetti AG, Wallisellen,Switzerland PERL Raw, unexpanded perlite AGStein Aktiengesellschaft fürSteinindustrie, Neuwied, Germany PP 0.02-millimeter polypropylenetransparent film Charter-Nex Films, Superior, WI, United States SUMAlkaline earth silicate fibers, mean fiber diameter of 3 – 4micrometers, available under the trade designation NUTEC Supermag NutecFibratec, S.A. de C.V., Mexico SW+ Alkaline earth silicate fibers with amean fiber diameter of 2.5-3.4 micrometers available under the tradedesignation “SUPERWOOL PLUS” Morgan Advanced Materials, Windsor, UnitedKingdom T255 Polyester/polyethylene bi-component staple fibers, 1.3 dtexand 6-millimeter length available under the trade designation T255Trevira GmbH, Bobingen, Germany VERM1 Vermucilite, 0.3 – 0.8 mm particlesize Cometals, Inc, New York, NY, United States VERM2 Vermucilite 0.3 –1.0 mm particle size Cometals, Inc, New York, NY, United States VERM3Vermucilite 3.0 – 8.0 mm particle size Cometals, Inc, New York, NY,United States WDS Microporous inorganic silicate insulation availableunder the designation WDS® Morgan Advanced Materials

Test Methods Hot-Side/Cold-Side Test 1 (HCST1)

In an MTS Insight 5 kN tensile test machine (obtained from MTS Insightof Eden Prairie, MN, United States), a bottom platen was heated to 600°C., and a sample was placed on top of it. The upper platen, with athermocouple embedded, was lowered such that the distance between thetwo platens was at 1.6 mm. The temperature increase at the cold-side wasrecorded with respect to time (continuously) until it reached 900seconds (15 minutes).

Hot-Side/Cold-Side Test 2 (HCST2)

In a 10 kN tensile test machine (obtained from ZWICKROELL of Ulm,Germany), a top platen was heated to 600° C. and a sample was placed ona bottom platen with a thermocouple embedded set at ambient temperature.A heat shield was used to cover the sample to ensure that it stayed atambient temperature. The heat shield was then removed, and the upperplaten was lowered with pressure held at 1 MPa. The time the sample tookreach a temperature of 150° C. (302° F.), designated t(150° C.), wasrecorded.

Shear Strength

The methods of ASTM273C 273M were followed. A five-minute shear speedwas used.

Thermal Conductivity Test

Thermal conductivity measurements values were obtained using a ThermalConstants Analyzer, Model TPS 2500S obtained from Hot Disk® AB ofGoteborg, Sweden. Measurements were taken by choosing the Isotropic/Bulk(Type I) module within the software. The measurements were run using aKapton 5465 sensor (Hot Disk®) having a diameter of 3.2 mm. As specifiedby the manual, the samples should have a lateral dimension that is 1.5to 2.0 times the radius of the sensor. The sample thickness should alsobe equivalent or greater than the radius of the sensor. To ensure thatthe thickness was sufficiently greater than the radius of the sensor,three to four layers of a sample were stacked on each side of the sensorand a small pressure was applied to ensure that layers were all incontact with one another.

Specified parameters were 1) measurement time in seconds and 2) heatingpower in mW. The sample temperature was inputted as the ambient roomtemperature. The measurement was then executed as defined in the TPSManual.

The results were analyzed by clicking on “Calculate” within the softwareand selecting the “Standard Analysis” option. After the measurement,several graphs were presented by the software, including the “Transient”graph and the “Residual” graph. The transient graph displays thetemperature increase of the sensor during the heating of the sample upto 200 points. The first pass at analyzing the results will start atpoint 10 and include everything up to point 200 on the transient. If theresidual graph does not look like a random scatter of points, a smallersubset of datapoints was used for the analysis. This was done bytrimming points from the beginning and end of the measurement. As arule, the result was not reliable if less than 50 points are used in theanalysis. In addition to satisfying the quality of the residual plot,several other numerical requirements were defined including “probingdepth (PD)”, “temperature increase (TI)”, “total to characteristic time(TCT)”, and “mean deviation (MD)” as specified in the manual. For thesespecifications: the PD must be less than the thickness of the sample,the TI must be between 0.4 K and 4.0 K, the TCT must be between 0.33 and1.0, and the MD must be a magnitude of 10-4 or better. If these fivecriteria were not met, the heating power and measurement times wereadjusted. The settings were iterated until an accurate measurement wasmade, where accuracy was defined by satisfying all the numericalrequirements laid out in the manual. Thermal conductivity values inW/m·K were measured and recorded for tested samples.

Examples 1 – 8 (EX1 – EX8) and Comparative Examples 1 – 2 (CE1 – CE2)

For Examples 1, 3, and 5-7, combinations of staple fibers by weightpercent (as identified in Table 2) were weighed and premixed by handbefore placing on top of a feeding belt. The fiber material wasprocessed (i.e., fed from the top) through an air-laid processer, likethat disclosed in U.S. Pat. No. 7,491,354, where the fibers were openedand dispersed into an air stream, then collected on a screen belt.Details of such air-laid processing apparatus and methods of using suchapparatus in forming air-laid webs can be found described in U.S. Pat.Nos. 9,580,848 (Henderson et al.), 9,475,034 (Vincent et al.), 7,491,354(Anderson), and 6,808,664 (Falk et al.). Fillers by weight percent (asidentified in Table 2) were top or side fed into the chamber or formingbox of the air-laid processor. A volumetric feeder coupled with anair-driven horn was used to distribute the fillers into the webuniformly. The sample was then sent through a forced-air convection ovenat 143.3° C. (290° F.) at a speed of 1.1 m/min.

For Examples 2 and 4, the process described in Example 1 of U.S. Pat.No. 5,869,010 (Langer) was followed. Samples were assembled containingfibers and fillers by weight percent as identified in Table 2 ratherthan the materials identified in U.S. Pat. No. 5,869,010.

For Example 8, Example A of U.S. Pat. No. 9,399,864 (Samanta et al.) wasfollowed with noted modifications. An aerogel slurry was prepared byadding 400 grams of Barlox 12 (obtained from Lonza Group of Basel,Switzerland) to 379 liters (100 gallons) of water at 43° C. (110° F.).The slurry was mixed. 200 grams of Foamaster 111 (obtained from BASFGroup of Ludwigshafen, Germany) was added and the slurry was mixed.EAF68 by weight percent (as identified in Table 2) was added and mixed.AG by weight percent (as identified in Table 2) was then added andmixed. The slurry was mixed for fifteen minutes and 200 grams of MOJO MP9307C was added and mixed. A fiber slurry was prepared by adding 717grams of Microstrand 110X-481(obtained from John Manville of Denver, CO,United States) to 2271 liters (600 gallons) of water. The slurry waspulped for 60 seconds at 500 rpm. T255 by weight percent (as identifiedin Table 2) was added and the slurry was pulped for 30 seconds at 500rpm. Another 1136 liters (300 gallons) of water was added to the slurry.757 liters (200 gallons) of the fiber slurry was mixed with 379 liters(100 gallons) of the aerogel slurry and SW+ by weight percent (asidentified in Table 2) was mixed in. The combined slurry was processedon a papermaking machine.

TABLE 2 Sample Compositions (Weight Percent) SW+ LDM T255 EAF68 PA AG K1WDS EXP EX1 20 20 16 0 4 40 0 0 0 EX2 0 62 0 8 0 0 30 0 0 EX3 20 20 16 04 0 0 40 0 EX4 0 52 0 8 0 0 0 0 40 CE1 35 35 30 0 0 0 0 0 0 EX5 15 15 300 0 40 0 0 0 CE2 92 0 8 0 0 0 0 0 0 EX6 72 0 8 0 0 20 0 0 0 EX7 52 0 8 00 40 0 0 0 EX8 59.5 0 2.5 8 0 30 0 0 0

The samples underwent HCST1 testing, and the results are represented inTable 3.

TABLE 3 Hot-side/Cold-side Temperature Test Results (Basis Weight = 600gsm) in Celsius (°C) Time (Minutes) EX1 EX2 EX3 EX4 CE1 EX5 CE2 EX6 EX7EX8 0 22.0 22.0 22.0 22.0 22.0 22.0 33.9 24.3 29.5 35.0 1 45.9 67.3 56.381.0 68.9 48.6 53.4 46.8 44.5 58.0 2 63.1 87.3 78.3 103.0 94.7 67.8 68.862.6 55.5 73.7 3 76.9 103.8 95.6 120.3 114.0 80.7 80.9 75.4 64.2 87.1 488.0 117.5 108.6 136.5 129.0 92.3 90.4 85.6 71.1 98.0 5 96.7 127.1 118.8146.6 140.7 101.6 94.5 90.0 74.0 106.7 6 104.4 134.6 126.5 155.3 150.5109.5 101.6 97.2 79.3 113.9 7 110.0 140.8 133.1 162.1 158.0 115.4 110.3105.8 85.5 120.1 8 115.3 145.7 138.5 168.1 164.6 119.6 114.9 110.2 88.8125.3 9 119.2 150.0 143.1 173.0 169.9 124.6 118.9 113.9 91.7 129.7 10122.6 153.7 147.0 177.3 174.5 128.1 122.2 117.0 94.1 133.6 11 125.7157.0 150.5 181.3 178.5 131.5 125.2 119.7 96.1 137.0 12 128.4 159.8153.4 184.5 181.9 131.9 127.6 121.9 97.8 139.9 13 130.8 162.4 156.1187.5 184.9 140.2 129.8 124.0 99.3 142.6 14 132.8 164.6 158.6 190.0187.5 137.7 131.8 125.8 100.6 145.0 15 134.7 166.5 160.8 192.0 189.9141.2 133.6 127.4 101.8 147.1

Examples 9 – 34 (EX9 – EX34) and Comparative Examples 3 – 8 (CE3 – CE8)

The ‘General Procedure for Preparing Fibrous Sheet’ as described in U.S.Pat. Application No. 2010/0115900 with material substitution asidentified in Table 4 was followed. Tap water (3 liters, 18° C.) and 60grams (g) of inorganic fibers and cleaned to a shot content of less than50 percent by weight) were added to a GT800 Classic blender (obtainedfrom Rotor Lips Ltd, Uetendorf, Switzerland). The blender was operatedon low speed for five seconds. The resultant slurry was rinsed into aRW16 mixing container equipped with a paddle mixer (obtained fromIKA-Werke GmbH, Staufen, Germany) using one liter of tap water (18° C.).The slurry was diluted with an additional one liter of tap water (18°C.). The diluted slurry was mixed at medium speed to keep solidssuspended. Defoaming agent (obtained under the trade designation“FOAMASTER 111” (0.3 g) from Henkel, Edison, N.J.) and ethylene-vinylacetate terpolymer latex (obtained under the trade designation “AIRFLEX600BP” (6.0 g, 55 percent by weight solids) from Air Products wereadded. Flocculent is added dropwise in amounts as indicated in Table 4.Thermally insulative particles were then added as indicated in Table 4.The mixer speed was increased and mixing continued for from 1 to 5minutes. The paddle mixer was removed, and the slurry was poured into a20 cm × 20 cm (8 inches × 8 inches) sheet former (obtained from WilliamsApparatus Co, Watertown, NY, United States) and drained. The surface ofthe drained sheet was rolled with a rolling pin to remove excess water.Then, the sheet was pressed between blotter papers at a surface pressureof 90-97 kPa (13-14 psi) for five minutes. The sheet was then dried at150° C. in a forced air oven for 10-15 minutes and allowed toequilibrate overnight while exposed to the ambient atmosphere. Thethickness and basis weight of the samples were measured at a constantpressure of 4.9 kPa, and are recorded in Table 5. For Examples 15 – 25(EX15 –EX25) the vermiculite material used in these samples were eitherpre-heated to permanently pre-expand the vermiculite, before being usedto make the samples, or post-heated to permanently post-expand thevermiculite, after the samples were made, at specific time andtemperature conditions. For EX21, the vermiculite was pre-heated at 300°C. for 6 hours before sample assembly. For EX22 and EX23, thevermiculite was heated at 450° C. for 30 minutes after sample assembly.For EX24, the vermiculite was pre-heated at 500° C. for 30 minutesbefore sample assembly. For EX25, EX33, and EX34, the vermiculite in thesample was pre-heated at 1000° C. for 30 minutes before sample assembly.

TABLE 4 Sample Compositions (Weight Percent) SW+ SUM EAF68 VERM1 EXVERMPERL EXPERL CE3 95 0 5 0 0 0 0 CE4 90 0 10 0 0 0 0 CE5 90 0 10 0 0 0 0CE6 90 0 10 0 0 0 0 CE7 90 0 10 0 0 0 0 CE8 90 0 10 0 0 0 0 EX9 50 0 545 0 0 0 EX10 50 0 5 45 0 0 0 EX11 50 0 5 45 0 0 0 EX12 50 0 5 45 0 0 0EX13 50 0 5 45 0 0 0 EX14 50 0 5 45 0 0 0 EX15 0 50 5 0 45 0 0 EX16 0 505 0 45 0 0 EX17 0 50 5 0 45 0 0 EX18 0 50 5 22.5 22.5 0 0 EX19 65 0 5 030 0 0 EX20 65 0 5 0 30 0 0 EX21 50 0 5 0 45 0 0 EX22 50 0 5 0 45 0 0EX23 50 0 5 0 45 0 0 EX24 50 0 5 0 45 0 0 EX25 50 0 5 0 45 0 0 EX26 0 238 0 0 0 69 EX27 0 23 8 0 0 0 69 EX28 0 23 8 0 0 0 69 EX29 0 47 6 0 0 047 EX30 0 22 6 0 0 0 72 EX31 0 70 5 0 0 25 0 EX32 0 20 5 0 0 75 0 EX3365 0 5 0 30 0 0 EX34 65 0 5 0 30 0 0

The samples underwent HCST2 testing and the results are represented inTable 5.

TABLE 5 Hot-side/Cold-side Temperature Test Results Thickness BasisWeight t(150° C.) (mm) (gsm) (seconds) CE3 4.17 643 297 CE4 2.68 413 162CE5 2.14 319 122 CE6 1.16 207 63 CE7 1.23 193 63 CE8 1.04 161 52 EX94.17 643 297 EX10 2.74 614 182 EX11 2.53 530 154 EX12 1.73 394 111 EX131.42 310 89 EX14 1.23 252 73 EX15 4.70 529 126 EX16 2.15 437 109 EX171.70 478 113 EX18 1.95 499 105 EX19 4.22 453 120 EX20 5.45 606 197 EX211.85 362 129 EX22 2.87 490 205 EX23 2.68 508 207 EX24 1.92 341 127 EX254.40 514 197 EX26 4.59 208 208 EX27 3.25 120 120 EX28 3.74 186 186 EX293.82 115 115 EX30 2.59 100 100 EX31 2.00 540 97 EX32 2.62 1197 139 EX332.80 450 116 EX34 3.42 550 141

Example 35 (EX35)

PP was laminated onto a sample as assembled in Example 5. Hand sampleswere hot pressed at 132° C. (270° F.) and 200 kPa on both sides. Theedges were manually sealed using an impulse sealer which was at 149° C.(300° F.), and heated for 2 seconds, cooled for 10 seconds, with all thesteps being conducted under a compressive force of 524 kPa (76 psi)pressure. The PP film thickness was 0.02 mm (1 mil). The 600 gsm sampleunderwent Shear Strength testing and the results are represented inTable 6.

Example 36 (EX36)

Hot melt adhesive H2345 was applied to the sample in Example 35 using aNordson Altablue Gridmelter with a 15.24 cm (6 inch) melt blown adhesivedie. The adhesive was heated at 193° C. (380° F.) and sprayed on to theweb at 206.8 kPa (30 psi) air pressure and 20 RPM pump rate. The 600 gsmsample underwent Shear Strength testing and the results are representedin Table 6.

Example 37 (EX37)

FB was spray coated onto a sample as assembled in Example 35 using aACCUSPRAY ONE Spray Gun System with PPS obtained from 3M Company of St.Paul, MN, United States. Hand samples were spray coated on one side andthen flipped to coat the other side. The 600 gsm sample underwent ShearStrength testing and the results are represented in Table 6.

Example 38 (EX38)

PKHH Phenoxy Resin obtained from Gabriel Performance Products of Akron,OH, United States was dissolved in a 50% solution of methyl ethyl ketone(MEK) to create an adhesive. The MEK was evaporated at room temperaturefor 60 minutes. Two coatings of the adhesive were applied onto one sideof a 0.076 mm (3 mil) PET film obtained from Dupont of Wilmington, DE,United States. Two coatings of the adhesive were applied onto a side ofanother 0.076 mm (3 mil) PET film. The thickness of the adhesive coatingwas 0.036 mm (1.4 mil). The adhesive coated PET sample films were placedonto the top and bottom side of a sample as assembled in Example 5. The600 gsm sample underwent Shear Strength testing and the results arerepresented in Table 6.

TABLE 6 Encapsulated Sample Test Results Shear Strength Example MPa EX350.27 EX36 0.27 EX37 0.26 EX38 1.28

Examples 39 - 40 (EX39 – EX40)

Samples were assembled using procedures described in Examples 9-16 withthe materials identified in Table 7. The thickness and basis weight ofthe samples were measured at a constant pressure of 4.9 kPa and arerecorded in Table 8. The samples underwent HCST2 testing and the resultsare represented in Table 8.

TABLE 7 Sample Compositions (Weight Percent) SW+ EAF68 VERM2 VERM3 EX3950 5 45 0 EX40 50 5 0 45

TABLE 8 Hot-side/Cold-side Temperature Test Results Thickness BasisWeight t(150° C.) (mm) (gsm) (seconds) EX39 1.78 405 84.7 EX40 2.65 723413.8

Examples 41 – 57 (EX41 – EX57)

Combinations of staple fibers by basis weight (as identified in Table 9)were weighed and processed through an air-laid processer. Details of theapparatus and methods of using the apparatus in forming air-laid websare described in U.S. Pat. Nos. 9,580,848 (Henderson et al.), 9,475,034(Vincent et al.), 7,491,354 (Anderson), and 6,808,664 (Falk et al.). Thecombined staple fibers were then processed again by the air-laidprocessor and a fumed silica filler was directly fed into the chamber ofthe air-laid processor by basis weight (as identified in Table 2). Ascrew feeder was used to distribute the fillers into the web uniformly.The web was sent through a forced-air convection oven at 148.89° C.(300° F.) at a speed between 0.25 m/min and 1.5 m/min. The thickness ofthe samples was between 0.5 to 15 mm.

The webs were then densified to a specified gap thickness using a hotpress. Polytetrafluoroethylene (PTFE) coated fiberglass fabric sheets(obtained from McMaster-Carr of Elmhurst, IL. United States) were placedon both sides of the samples and the samples were placed between two hotplates maintained at a temperature of 148.89° C. (300° F.). Pressure wasapplied for 30 to 120 seconds to activate the bi-component fibers(T255). The densified sample was then immediately placed between twoplates maintained at room temperature under a pressure for 30 to 120seconds, to set the web to the desired thickness.

TABLE 9 Sample Compositions (gsm) SW+ T255 FS EX41 256 64 80 EX42 192 48160 EX43 128 32 240 EX44 384 96 160 EX45 288 72 320 EX46 192 48 480 EX47640 160 200 EX48 480 120 400 EX49 480 120 400 EX50 480 120 400 EX51 480120 400 EX52 480 120 400 EX53 480 120 400 EX54 320 80 600 EX55 768 192240 EX56 576 144 480 EX57 384 96 720

The samples underwent HCST2 testing, and the results are represented inTable 10. The actual thickness of the samples was measured by ASTMD5736-95 with the fiberglass fabric sheets removed. The plate pressurewas calibrated at 0.002 psi (13.790 Pascal).

TABLE 10 Hot-side/Cold-side Temperature Test Results Target ThicknessActual Thickness Target Basis Weight Actual Basis Weight t(150° C.) (mm)(mm) (gsm) (gsm) (seconds) EX41 1.00 0.99 400 387 35 EX41 1.00 0.97 400337 53 EX42 1.00 1.09 400 324 287 EX43 2.00 1.94 800 547 277 EX44 2.001.96 800 697 737 EX45 2.00 2.09 800 657 3600 EX47 3.00 2.92 1000 837 230EX48 3.00 2.8 1000 743 3600 EX49 2.00 2.02 1000 953 799 EX50 3.00 2.831000 930 3600 EX51 4.00 3.56 1000 857 3600 EX52 6.00 5.94 1000 907 3600EX53 8.00 7.78 1000 933 3600 EX54 3.00 2.80 1000 707 3600 EX55 4.00 3.961200 1077 685 EX56 4.00 3.90 1200 1097 3600 EX57 4.00 3.90 1200 873 3600

Densities of 1000 gsm samples containing 40% fumed silica (representedin EX48 -EX53) were computed by dividing the actual basis weight (gsm)by the actual thickness (mm). Density and the cold side temperaturerecorded after 3600 seconds of HCST2 testing for EX48 –EX53 isrepresented in Table 11. The table is organized in descending order bymeasured cold side temperatures.

TABLE 11 Density vs. Cold Side Temperature Density Cold Side Temperature(gsm/mm) °C EX49 472 180.9 EX51 241 141.7 EX53 120 140.2 EX52 153 137.3EX50 329 134.6 EX48 265 130.8

Thermal conductivity testing was performed, and the results arerepresented in Table 12.

TABLE 12 Thermal Conductivity Test Results Thermal Conductivity W/m·KEX47 0.0531 EX49 0.0708 EX50 0.0481 EX52 0.0508

Surprisingly, it has been found that fumed silica has a higher thermalconductivity than silica aerogel. It is believed that the thermalconductivity of the nonwoven fibrous thermal insulation without thefumed silica particles (i.e., the fiber matrix) is lower than the samefiber matrix with the fumed silica particles.

ADDITIONAL EMBODIMENTS Battery Cell Thermal Runaway Barrier Embodiments

1. A thermal runaway barrier operatively adapted (i.e., designed,configured, shaped and/or dimensioned) or otherwise suitable for beingdisposed between adjacent battery cells (e.g., prismatic- or pouch-typebattery cells) of a battery module or assembly (i.e., a series ofbattery cells stacked together in a row) such as that used to power anelectric motor (e.g., like that used in an electric or hybrid vehicle)and for preventing, stopping or at least significantly slowing down athermal runaway event within the battery module or assembly or betweenadjacent battery modules or assemblies, the thermal runaway barriercomprising:

-   only one or more layers of a dry-laid or wet-laid nonwoven fibrous    thermal insulation (e.g., in the form of a mat, sheet, strip, or    three-dimensional thin-walled structure) comprising a fiber matrix    of ceramic or otherwise nonmetallic (i.e., not a metal, metal alloy,    or metal composite) inorganic fibers;-   thermally insulative ceramic or otherwise nonmetallic (i.e., not a    metal, metal alloy, or metal composite) inorganic particles of    irreversibly or permanently expanded expandable inorganic material    (e.g., intumescent materials such as vermiculite, perlite mineral    dispersed evenly, uniformly, generally or otherwise throughout or to    the extent permitted by the manufacturing process (e.g., there can    be a little sedimentation of the particles on the bottom of the mat    in both the dry laid and wet laid processes) within the fiber    matrix, and an organic or inorganic binder (e.g., organic or    inorganic adhesive binder, organic or inorganic binder fibers that    are needle punched, stitched or otherwise mechanically entangled    into the fiber matrix so as to hold together the fiber matrix, etc.)    dispersed evenly, uniformly, generally or otherwise throughout or to    the extent permitted by the manufacturing process within the fiber    matrix so as to bond together the inorganic filler particles and    inorganic fibers or otherwise hold together the fiber matrix for as    long as needed to at least survive the degree of handling required    (e.g., during the encapsulation process) before being installed    between battery cells;-   an optional organic (e.g., polymeric, paper, etc.) encapsulation    layer (e.g., one layer or multiple opposing sandwiching layers, with    each layer being in the form of a film, coating, organic fibrous    nonwoven or woven fabric, etc.) enclosing or otherwise encapsulating    all of, a majority of or a portion of at least one or both major    faces and preferably also all of, a majority of or a portion of the    peripheral edge of the layer of nonwoven fibrous thermal insulation    so as to prevent or significantly reduce the shedding or loss of    inorganic fibers or particles from the encapsulated layer of    nonwoven fibrous thermal insulation; and-   an optional inorganic (e.g. glass fiber woven fabric of 25 – 80    g/m²) encapsulation layer (e.g., one layer or multiple opposing    sandwiching layers, with each layer being in the form of an    inorganic coating or fibrous nonwoven or woven fabric, etc.)    enclosing or otherwise encapsulating all of, a majority of or a    portion of at least one or both major faces and preferably also all    of, a majority of or a portion of the peripheral edge of the layer    of nonwoven fibrous thermal insulation so as to prevent or    significantly reduce the shedding or loss of inorganic fibers or    particles from the encapsulated layer of nonwoven fibrous thermal    insulation.

The reduction of inorganic fiber or particle shedding is significant,when the number of inorganic fibers or particles lost is less than 10%,5% or 1% by weight percent of the original fiber or particle content ofthe layer of nonwoven fibrous thermal insulation. The thinner theorganic encapsulation layer (i.e., the lower the organic content of thebarrier) the better the hot/cold test results.

The present thermal runaway barrier may also be used between batterymodules or assemblies.

Inorganic binders, organic binders, or a combination of both can beuseful according to the present invention and may include, e.g., thosedisclosed in US 8,834,759. An example of an inorganic binder useful inboth dry-laid or wet-laid fiber processing can include particles ofsilicone that convert to fusible silica when heated. Anorganic-inorganic hybrid binder may also be useful such as, e.g.,WACKER® MQ 803 TF, which is a co-hydrolysis product of tetra-alkoxysilane (Q unit) and trimethyl-alkoxy silane (M unit). The chemicalstructure of WACKER® MQ 803 TF can be seen as a three dimensionalnetwork of polysilicic acid units which are end-blocked withtrimethylsilyl groups. Some residual ethoxy and hydroxy functions arepresent. The average molecular weight can be exactly controlled by theratio of M and Q units. This ratio approx. is 0.67 for WACKER® MQ 803TF.

Exemplary binder fibers include the use of bicomponent core-sheathpolymeric fibers in a dry-laid process. In a wet-laid process, ethylenevinyl acetate latex dispersion binder, bicomponent core-sheath polymericfibers, or a combination of both can be used. When a polymeric binderfiber is used, the binder can be activated by heating and compressingthe nonwoven fibrous thermal insulation material. A combination oforganic and inorganic binders can also be used.

As used herein, the term “inorganic” refers to ceramic or otherwisenonmetallic (i.e., not a metal, metal alloy, or metal composite)inorganic material.

A “thermal runaway” is when a battery cell experiences an exothermicchain reaction causing the phenomenon of an uncontrollable temperaturerise of the battery cell. The exothermic chain reaction may be caused,for example, by over-heating of the battery cell, over-voltage of thebattery cell, and mechanical puncture of the battery cell, among otherreasons.

A “thermal propagation” is when a battery cell thermal runaway causesthe remaining battery cells in a battery pack or system to undergo thethermal runaway phenomenon.

A “thermal runaway event” refers to the overheating of one battery cell,in a container of battery cells, causing a chain reaction of adjacentbattery cells overheating, and potentially exploding or catching fire,until the number of overheated battery cells reaches a critical point ofpropagation resulting in all or more than half of the battery cells inthe module or assembly of modules being destroyed. Factors that cancause a battery cell to overheat include: physical damage, applying overvoltage, overheating (internal battery cell shorting).

As the energy density of a battery cell increases, the temperature atwhich the battery cell starts to malfunction (e.g., from at least losingits efficiency or failing to function up to igniting, burning orexploding) decreases. Likewise, as the energy density of the batterycell decreases, the temperature at which the battery cell starts tomalfunction increases. For example, with a controlled ramping up of thetemperature, NMC811 type battery cells tend to start malfunctioning oreven blow up when the temperature reaches around 120° C. to 130° C.,while NMC622 type battery cells start to malfunction or even blow upwhen they reach a temperature of around 180° C. The correspondingtemperature is higher for battery cells with lower energy densities(e.g., NMC532 and NMC433 type battery cells). With physically largerbattery cells or when the temperature is rapidly increased, thermaldiffusion through the battery cell can result in the localizedtemperature taking longer to get up to the critical point. It isbelieved that this thermal diffusion effect can cause the actualtemperature at which the battery cell starts to malfunction or blow upto be somewhat higher. It can be desirable for the thermal runawaybarrier of the present invention to prevent an adjacent battery fromreaching a temperature in the range of from about 130° C. up to about150° C.

As used herein, “preventing” a thermal runaway event refers topreventing the overheating of a single battery cell from causing theoverheating of battery cells that are adjacent to the single batterycell. The barrier is considered to prevent a thermal runaway event, whenadjacent battery cells do not reach above 130° C., 135° C., 140° C.,145° C. or 150° C.

As used herein, “stopping” a thermal runaway event refers to theoverheating of a battery cell only causing adjacent battery cells (i.e.,three, two or even only one battery cell away on either side of theoverheating battery cell) to overheat and the remaining battery cells inthe battery module or assembly do not overheat.

As used herein, “slowing down” a thermal runaway event refers to thethermal runaway event being slowed down at least long enough to allowpersonnel adjacent to the battery module or assembly (e.g., an occupantinside of an electric vehicle passenger compartment) to escape to a safedistance away from the battery module or assembly, before being injuredby the thermal runaway event. Once a battery cell malfunctions (e.g., ison fire or overheats to the point of not functioning) and a thermalbarrier is in place between battery cells, the time for any adjacentbattery cells to propagate the malfunction (e.g., catching fire oroverheating) is at least more than 5 minutes, and preferably more than10 minutes or even 20 minutes.

The inorganic particles can include, e.g., particles of irreversibly orpermanently expanded intumescent material, irreversibly or permanentlyexpanded perlite mineral, etc.. Such inorganic particles that containvoids such as, e.g., those found in irreversibly or permanently expandedvermiculite are particularly desirable. Particles of irreversibly orpermanently expanded perlite mineral also contain voids, but perlitemineral is harder and less compressible than vermiculite mineral.

As used herein, an irreversibly or permanently expanded expandableparticle (e.g., particle of an intumescent material such as vermiculiteand perlite mineral) refers to a particle that has been heated to atemperature and for a time that causes the particle to irreversibly orpermanently expand to at least 10% and up to 100% of its expandability,either by being pre-expanded before being used to form the thermalrunaway barrier, or post-expanded after it is incorporated into thenonwoven fibrous thermal insulation.

Intumescent particles (e.g., vermiculite particles) can be permanentlyexpanded by overheating the particles to beyond the point ofreversibility (e.g., in the range of from about 350° C. up to about1000° C. for vermiculite). Such a permanently expanded intumescentparticle (e.g., vermiculite particle) can have an expanded accordion orworm-like structure that is easier to break apart into smallerparticles, compared to the same particle in its unexpanded state,because of its elongated geometry, lower density and lower mechanicalstability. As the heating temperature increases, the degree of permanentexpansion of the particle increases (i.e., the particles can get largerand/or longer). It may also be desirable to use vermiculite that hasbeen permanently expanded by a chemical treatment method (see, e.g.,“Chemical Exfoliation of Vermiculite and the Production of ColloidalDispersions”, G.F. Walker, W.G.Garrett, Science 21Apr1967: Vol. 156,Issue 3773, pp. 385-387, DOI: 10.1126/science. 156.3773.385; andhttps://science.sciencemag.org/content/156/3773/385.abstract).

Because they are easier to break apart in their expanded state, it canbe desirable to post-expand the intumescent particles, after theunexpanded intumescent particles have been incorporated into thenonwoven fibrous thermal insulation. Even if gentle processing isemployed so as not to substantially break them apart, it is believedthat incorporating pre-expanded intumescent particles into the nonwovenfibrous thermal insulation can still result in the expanded particlesbecoming oriented into the plane (i.e., x-axis, y-axis, and/ortherebetween) of the insulation. For example, with pre-expandedvermiculite particles, the elongated particles can become generallyaligned with the fibers in the longitudinal or downstream direction(i.e., y-axis), rather than in the thickness direction (i.e., z-axis),of the nonwoven fibrous thermal insulation.

In contrast, when they are post-expanded (i.e., after the nonwovenfibrous thermal insulation is made with unexpanded intumescentparticles), the expanded intumescent particles are not orientedprimarily in the plane of the insulation. Unexpanded intumescentparticles typically have a more uniform structural geometry (i.e., havean aspect ratio closer to 1) compared to the same particles in itsexpanded state. It is believed that this more uniform structuralgeometry is less likely to be influenced by the alignment of the fibersduring the formation of the nonwoven fibrous thermal insulation. As aresult, the post-expanded intumescent particles are more likely to beoriented isotropically within the nonwoven fibrous thermal insulation.For example, with post-expanded vermiculite particles, the elongatedparticles can become aligned in the thickness direction (i.e., z-axis),in plane (i.e., x-axis, y-axis, and/or therebetween), or off-axisthereof. It is believed this difference between the orientation ofpre-expanded particles versus post-expanded particles is caused by theunexpanded particles having a more uniform structural geometry than thatexhibited while in their expanded state.

2. The thermal runaway barrier according to embodiment 1, wherein thelayer of nonwoven fibrous thermal insulation contains an amount ofinorganic fibers in the range of from as low as about 15 to 19% up to ashigh as about 70, 75, 80, 85 or 90%, by weight of the layer of nonwovenfibrous thermal insulation.

3. The thermal runaway barrier according to embodiment 1 or 2, whereinthe layer of nonwoven fibrous thermal insulation contains an amount offiber shot in the range of from about 3% up to about 60% by weight ofthe amount of inorganic fibers in the layer of nonwoven fibrous thermalinsulation.

In one embodiment, if no insulative particles are added, then inorganicfiber content is 95.2% by weight in dry-laid and 95.5% by weight inwet-laid. At the lowest level of insulative particle (e.g., aerogelparticle) loading, the inorganic fiber content is 72% by weight fordry-laid and wet-laid. For dry laid nonwoven fibrous thermal insulation,the fibers are opened (i.e., the bulk fibers are separated, made lessdense), which may remove some shot. For wet laid nonwoven fibrousthermal insulation, the fibers are wet cleaned, which removes more shotthan is removed by the dry laid opening process. There is about 40% shotin uncleaned SuperWool Plus from Morgan, actual fibrous material contentis 19-43% in the nonwoven fibrous thermal insulation. It can bedesirable for the nonwoven fibrous thermal insulation to have a fibercontent in the range of from about 10% up to about 80%. The lower amountof fiber would require a higher amount of organic binder. Otheradditives (e.g., flame retardant materials, endothermic materials,infra-red reflective materials, etc.) may be included.

4. The thermal runaway barrier according to any one of embodiments 1 to3, wherein the layer of nonwoven fibrous thermal insulation contains anamount of the thermally insulative inorganic particles in the range offrom as low as about 10%, 15%, 20%, 25%, 30% or 35% up to as high asabout 40%, 45%, 50%, 55% or 60%, by weight of the layer of nonwovenfibrous thermal insulation. For example, a particle content as high as60% can be achieved using a dry-laid process, and as high as 50% using awet laid process.

5. The thermal runaway barrier according to any one of embodiments 1 to4, wherein the layer of nonwoven fibrous thermal insulation contains anamount of organic binder in the range of from as low as about 2.5%,3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0% or 6.5% up to as high as about7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, or 10.0%, by weight of the layer ofnonwoven fibrous thermal insulation.

6. The thermal runaway barrier according to any one of embodiments 1 to5, wherein the layer of nonwoven fibrous thermal insulation has aninstalled (i.e., compressed) thickness in the range of from about 0.5 mmup to less than 5.0 mm. In particular, the installed (i.e., compressed)thickness in the range of from about 0.5 mm up to about 2.5 mm, wherethe lower limit can be about 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, and the upper limit can beabout 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm,2.4 mm or 2.5 mm. In some applications, the installed thickness may evenbe as high as about 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm orless than 5.0 mm. The installed thickness of the layer of nonwovenfibrous thermal insulation is almost always less than its uninstalled(i.e., uncompressed) thickness. The performance of the thermal runawaybarrier is measured when it is in its installed (i.e., compressed)condition.

7. The thermal runaway barrier according to any one of embodiments 1 to6, wherein the layer of nonwoven fibrous thermal insulation has anuninstalled (i.e., uncompressed) thickness in the range of from about1.0 mm up to less than 8.0 mm, where the lower limit can be about 1.0mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, or 3.5 mm, and theupper limit can be about 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm,4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm,7.5 mm, or 8.0 mm. The uncompressed thickness of the layer of nonwovenfibrous thermal insulation is always greater than its installedthickness.

8. The thermal runaway barrier according to any one of embodiments 1 to7, wherein the layer of nonwoven fibrous thermal insulation has a basisweight in the range of from as low as about 250 g/m² up to as high asabout 1000 g/m². Depending on the composition of the thermal runawaybarrier, it can be desirable for the basis weight to be in the range offrom about 250 g/m² to about 400 g/m² (e.g., 300 g/m², 350 g/m²) for agap between adjacent battery cells in the range of from about 0.75 mm upto about 1.25 mm. Depending on the composition of the thermal runawaybarrier, it can also be desirable for the basis weight to be in therange of from about 300 g/m² up to about 550 g/m² for a gap betweenadjacent battery cells in the range of from about 0.75 mm to about 2.5mm., and up to as high as about, For gaps between adjacent battery cellsin the range of from about 2.5 mm up to less than 5.0 mm, it can bedesirable for the basis weight to be in the range of from about 600 g/m²up to about 1000 g/m² (e.g., about 650 g/m², 700 g/m², 750 g/m², 800g/m², 850 g/m², 900 g/m², 950 g/m² or 1000 g/m²). Desirable results havebeen achieved with thermal runaway barriers using thermally insulativeinorganic particles of irreversibly or permanently expanded vermiculite,where the nonwoven fibrous thermal insulation has a basis weight ofabout 450 g/m² or 550 g/m² for a gap in the range of from about a 1.50mm up to about 2.5 mm.

In one embodiment, the thermally insulative inorganic particles areparticles of irreversibly or permanently expanded vermiculite, and thelayer of nonwoven fibrous thermal insulation has a basis weight of 450g/m² for an installed gap between adjacent battery cells in the range offrom about a 1.50 mm up to about 2.5 mm.. In another embodiment, thethermally insulative inorganic particles are particles of irreversiblyor permanently expanded vermiculite, and the layer of nonwoven fibrousthermal insulation has a basis weight of 550 g/m² for an installed gapbetween adjacent battery cells in the range of from about a 1.50 mm upto about 2.5 mm.

9. The thermal runaway barrier according to any one of embodiments 1 to8, wherein the layer of nonwoven fibrous thermal insulation has a basisweight in the range of from about 250 g/m² up to about 400 g/m².

In a particular embodiment, for example, a basis weight in the range offrom about 300 g/m² up to 400 g/m² can be desirable, when the thermallyinsulative inorganic particles are particles of irreversibly orpermanently expanded vermiculite and the gap is about 1 mm. When the gapis about 2.0 mm, a basis weight in the range of from about 800 g/m² upto about 1000 g/m² may be desirable.

10. The thermal runaway barrier according to any one of embodiments 1 to9, wherein the thermally insulative inorganic particles are made from orat least comprise particles of one or any combination of the materialsselected from the group consisting of irreversibly or permanentlyexpanded vermiculite (i.e., vermiculite that has been heated to atemperature and for a time that causes the vermiculite particles toirreversibly or permanently expand to at least 10% and up to 100% of itsexpandability, either by being pre-expanded before being used to formthe barrier, or post-expanded after it is in the nonwoven fibrousthermal insulation), irreversibly or permanently expanded perlite (i.e.,perlite that has been heated to a temperature and for a time that causesthe perlite particles to irreversibly or permanently expand to at least10% and up to 100% of its expandability, either by being pre-expandedbefore being used to form the barrier, or post-expanded after it is inthe nonwoven fibrous thermal insulation), and irreversibly orpermanently expanded clay.

Expanded clay is a lightweight particle or aggregate, which can be madeby heating clay to around 1,200° C. (2,190° F.) in a rotary kiln. Theyielding gases expand the clay by thousands of small bubbles formingduring heating producing a honeycomb structure. Expanded clay can havean approximately round or potato shape due to circular movement in thekiln and is available in different sizes and densities. Expanded clayshave been used to make lightweight concrete products (see, e.g., thewebsite:https://www.archiexpo.com/architecture-design-manufacturer/expanded-clay-aggregate-concrete-23000.html)and other uses. Expanded clay is most commonly known under the brandnames LECA (acronym of light expanded clay aggregate) or LIAPOR (porouslias clay), also known as Hydroton and under the non-proprietary termsfired clay pebble, grow rocks, expanded clay or hydrocoms, are smallglobes of burnt and expanded clay (see, e.g., the website:https://www.sciencedirect.com/topics/engineering/expanded-clay-aggregate).

It can be desirable for the thermal runaway barrier to further includeother thermally insulative inorganic particles such as, e.g., particlesof one or any combination of the materials selected from the groupconsisting of inorganic aerogel, xerogel, hollow or porous ceramicmicrospheres, unexpanded vermiculite, fumed silica, otherwise poroussilica, unexpanded perlite, pumicite, diatomaceous earth, titania andzirconia.

11. The thermal runaway barrier according to any one of embodiments 1 to10, wherein the inorganic fibers of the fiber matrix are selected fromthe group of fibers consisting of alkaline earth silicate fibers,refractory ceramic fibers (RCF), polycrystalline wool (PCW) fibers,basalt fibers, glass fibers and silicate fiber. Glass fibers and silicafibers typically do not contain any or only nominal shot particles. PCWtypically contains a max of 5% shot particles, while alkaline earthsilicate (AES) fibers contain up to 60% shot particles when uncleanedand as low as about 10 -30% minimum shot particles when cleaned).

12. The thermal runaway barrier according to any one of embodiments 1 to11, wherein the organic binders are in the form of polymer fibers (e.g.,PE/PET, PET, FRPET), dry polymer powder (e.g., LDPE, polyamide, epoxyresin powder (3M SCOTCHCAST 265, 3M SCOTCHKOTE 6258)) or a liquid binder(e.g., acylic latex, ethylene vinyl acetate (EAF68) latex, silicone,polyurethane etc.).

13. The thermal runaway barrier according to any one of embodiments 1 to12, wherein the layer of nonwoven fibrous thermal insulation isencapsulated by the organic encapsulation layer.

14. The thermal runaway barrier according to embodiment 13, wherein theorganic encapsulation layer has at least one vent hole formedtherethrough that is located and sized to allow expanding gas (e.g.,air) contained within the thermal runaway barrier to escape from theorganic encapsulation, such that the structural integrity of the organicencapsulation layer is kept intact (i.e., the layer of nonwoven fibrousthermal insulation remains completely, mostly or at least significantlyencapsulated by the organic encapsulation layer), when the thermalrunaway barrier is compressed during the assembly of the battery cellmodule (e.g., a stack of battery cells) or when the thermal runawaybarrier heats up (e.g., during the normal operation or overheating ofthe adjacent battery cells). Each vent hole can be in the shape of arectangle (e.g., see FIG. 8 ), circle, oval or any other shape desiredor combination thereof. One or more or each vent hole can be in the formof a notch that projects from a side edge of the encapsulation towardsthe center of the thermal runaway barrier (e.g., see the left side venthole 54 in FIG. 8 and the vent holes 54 in FIG. 7 ). Alternatively, oneor more or each vent hole can be formed interior of the side edge of theencapsulation and adjacent to the nonwoven thermal insulation (see theright side vent hole 52 in FIG. 8 and the vent holes 52 in FIG. 6 ). Inaddition, one or more or each vent hole can be formed through theencapsulation layer on only one side (see vent hole 52 on the right sideof FIG. 6 ) or both sides (see vent hole 52 on the left side of FIG. 6 )of the nonwoven fibrous thermal insulation. It can also be desirable foreach vent hole to be in the form of a plurality of small perforation,that are clustered together (e.g., like a screen, sieve or colander) toprovide the desired exit opening area.

15. The thermal runaway barrier according to embodiment 13 or 14,wherein the thermal runaway barrier has a top edge, a bottom edge andopposite side edges, and the at least one vent hole is located along theperiphery of one or both opposite side edges.

16. The thermal runaway barrier according to any one of embodiments 13to 15, wherein the at least one vent hole provides an exit openingthrough the organic encapsulation layer having an opening area in therange of from about 2 mm² up to about 15 mm². It is contemplated thatany particular area within this range, or any narrower range within thisrange, could be desirable.

17. The thermal runaway barrier according to any one of embodiments 13to 16, wherein the organic encapsulation layer is in the form of acontinuous layer, a discontinuous layer (e.g., having perforations,through-holes, or porosity that would allow a gas to penetrate throughthe organic layer), or a combination of both. In addition, the organiclayer can be in the form of an organic (e.g., polymeric) film, scrim,woven or nonwoven fabric, adhesive (e.g., a thermoplastic or hot-meltadhesive) layer or a combination thereof. One example of the organiclayer is a polymeric film (e.g., a co-polyester polymeric film).

18. The thermal runaway barrier according to any one of embodiments 13to 17, wherein the organic encapsulation layer is a calendared layer,hot-melt coated layer, spray coated layer, dip coated layer, orlaminated layer (e.g., with by use of a pressure sensitive adhesive orother adhesive).

19. The thermal runaway barrier according to any one of embodiments 13to 18, wherein the layer of nonwoven fibrous thermal insulation has aperipheral edge, and the organic encapsulation layer is sealed aroundthe peripheral edge.

20. The thermal runaway barrier according to any one of embodiments 1 to19, wherein the layer of nonwoven fibrous thermal insulation passes atleast the V-2 or V-1 level, and preferably the V-0 level, of the belowUL94 V0 Flammability Test.

Flammability Test

The test was performed using the UL-94 standard, the Standard for safetyof Flammability of Plastic Materials for Parts in Devices and Appliancestesting. The UL-94 standard is a plastics flammability standard releasedby Underwriters Laboratories of the United States. The standarddetermines the material’s tendency to either extinguish or spread theflame once the specimen has been ignited. The UL-94 standard isharmonized with IEC 60707, 60695-11-10 and 60695-11-20 and ISO 9772 and9773. A 75 mm × 150 mm sample was exposed to a 2 cm, 50 W tirrel burnerflame ignition source. The test samples were placed vertically above theflame with the test flame impinging on the bottom of the sample. Foreach sample, the time to extinguish was measured and V ratings areassigned. V ratings are a measure to extinguish along with the samplenot burning to the top clamp or dripping molten material which wouldignite a cotton indicator, as shown in Table 1 below.

TABLE 1 UL94 classification (V rating). UL 94 classification V-0 V-1 V-2Burning stops within 10 s 30 s 30 s Drips of burning material allowed(ignites cotton ball) No No Yes Total burn of sample No No No

21. The thermal runaway barrier according to any one of embodiments 1 to20, wherein the thermally insulative inorganic particles are made fromor at least comprise particles of irreversibly or permanently expandedintumescent material.

22. The thermal runaway barrier according to embodiment 21, wherein theexpanded intumescent material has been irreversibly or permanentlyexpanded in the range of from at least about 10%, 20%, 30%, 40%, 50%,60%, 70%, 80% or 90% up to 100% of its expandability.

23. The thermal runaway barrier according to any one of embodiments 1 to20, wherein the thermally insulative inorganic particles are made fromor at least comprise particles that are irreversibly or permanentlyexpanded vermiculite particles.

24. The thermal runaway barrier according to embodiment 23, wherein theexpanded vermiculite particles have been irreversibly or permanentlyexpanded in the range of from at least about 10%, 20%, 30%, 40%, 50%,60%, 70%, 80% or 90% up to 100% of its expandability.

25. The thermal runaway barrier according to any one of embodiments 1 to24, wherein the thermally insulative inorganic particles furthercomprise particles of fumed silica.

26. The thermal runaway barrier according to embodiment 25, wherein theparticles of fumed silica have a surface area in the range of from about100 m²/g up to about 400 m²/g.

27. A thermal runaway barrier assembly comprising a plurality of thethermal runaway barriers according to any one of embodiments 1 to 26,wherein the plurality of thermal runaway barriers are provided (a) in acontainer (e.g., a cardboard or other box) in the form of a stack, (b)disposed end-to-end in series, with one major face of each thermalrunaway barrier being adhered onto a major adhesive surface of a lengthof single-sided or double-sided adhesive tape (When a double-sidedadhesive tape is used, the opposite major adhesive surface of the tapecan be protected by a release liner), or (c) disposed end-to-end inseries in the form of a tape, with the one or more layers of nonwovenfibrous thermal insulation of each thermal runaway barrier beingdisposed end-to-end and sandwiched or otherwise encapsulated between twoopposing lengths of organic (e.g., polymeric) encapsulation layers(e.g., in the form of two opposing films, coatings, fibrous fabrics,etc.).

Battery Cell Module Embodiments

28. A battery cell module or assembly for an electric vehicle, thebattery cell module or assembly comprising:

-   a plurality of battery cells disposed in a housing; and-   a plurality of thermal runaway barriers according to any one of    embodiments 1 to 27,-   wherein the battery cells are lined up in a row or stack, with one    thermal runaway barrier being disposed between each pair of adjacent    battery cells or between a predetermined number of battery cells.

Method of Making Battery Cell Thermal Runaway Barrier Embodiments

29. A method of making the thermal runaway barrier according to any oneof embodiments 1 to 27, wherein the method comprises forming the layerof nonwoven fibrous thermal insulation using a wet-laid process ordry-laid process.

30. The method according to embodiment 29, further comprising:

-   providing thermally insulative inorganic particles that are made    completely of, mostly of or at least comprise unexpanded expandable    particles (e.g., unexpanded intumescent particles such as unexpanded    vermiculite particles or unexpanded perlite particles);-   disposing the thermally insulative inorganic particles so as to be    evenly or uniformly distributed throughout or within the layer of    nonwoven fibrous thermal insulation; and-   heating the unexpanded expandable particles (e.g., intumescent    particles) to a temperature and for a time that causes the    unexpanded expandable particles to irreversibly or permanently    expand,-   wherein the heating occurs before or after the unexpanded expandable    particles are disposed within the layer of nonwoven fibrous thermal    insulation.

31. The method according to embodiment 30, wherein the heating occursafter the unexpanded expandable particles are disposed within the layerof nonwoven fibrous thermal insulation.

32. The method according to embodiment 30 or 31, wherein the heatingcauses the unexpanded intumescent particles to irreversibly orpermanently expand in the range of from at least about 10%, 20%, 30%,40%, 50%, 60%, 70%, 80% or 90% up to 100% of their expandability.

33. The method according to any one of embodiments 30 to 32, wherein theunexpanded expandable particles include unexpanded intumescent particles(e.g., vermiculite particles, unexpanded perlite particles, or acombination of both).

34. The method according to embodiment 29, further comprising:

-   providing thermally insulative inorganic particles that are made    completely of, mostly of, or at least comprise irreversibly or    permanently pre-expanded expandable particles (e.g., irreversibly or    permanently pre-expanded intumescent particles of vermiculite or    perlite); and-   disposing the thermally insulative inorganic particles so as to be    evenly or uniformly distributed throughout or within the layer of    nonwoven fibrous thermal insulation,-   wherein the pre-expanded particles where formed by heating    unexpanded expandable particles to a temperature and for a time that    causes the unexpanded expandable particles to irreversibly or    permanently expand, before the thermally insulative inorganic    particles are disposed within the layer of nonwoven fibrous thermal    insulation.

35. The method according to embodiment 34, wherein the pre-expandedexpandable particles are intumescent particles that are irreversibly orpermanently expanded in the range of from at least about 10%, 20%, 30%,40%, 50%, 60%, 70%, 80% or 90% up to 100% of their expandability.

36. The method according to embodiment 34 or 35, wherein thepre-expanded expandable particles include pre-expanded vermiculiteparticles, pre-expanded perlite particles, or both.

This invention may take on various modifications and alterations withoutdeparting from its spirit and scope. For example, it is believed thatmicrowave heating can be used to irreversibly or permanently expand theparticles made from intumescent materials. It is also believed thatusing microwave energy, rather than baking in an oven, can result in amore uniform expansion of the intumescent particles within the fibermatrix. Accordingly, this invention is not limited to theabove-described but is to be controlled by the limitations set forth inthe following embodiments and any equivalents thereof. This inventionmay be suitably practiced in the absence of any element not specificallydisclosed herein. All patents and patent applications cited above,including those in the Background section, are incorporated by referenceinto this document in total.

1. A thermal runaway barrier operatively adapted for being disposedbetween battery cells of a battery assembly and for at leastsignificantly slowing down a thermal runaway event within the batteryassembly, said thermal runaway barrier comprising: a layer of a nonwovenfibrous thermal insulation comprising a fiber matrix of inorganicfibers; thermally insulative inorganic particles of irreversibly orpermanently expanded expandable inorganic material dispersed within thefiber matrix, and a binder dispersed within the fiber matrix so as tohold together the fiber matrix; an optional organic encapsulation layerenclosing the layer of nonwoven fibrous thermal insulation; and anoptional inorganic encapsulation layer enclosing the layer of nonwovenfibrous thermal insulation.
 2. The thermal runaway barrier according toclaim 1, wherein the layer of nonwoven fibrous thermal insulationcontains an amount of fiber shot in the range of from about 3% up toabout 60% by weight of the amount of inorganic fibers in the layer ofnonwoven fibrous thermal insulation.
 3. The thermal runaway barrieraccording to claim 1, wherein the layer of nonwoven fibrous thermalinsulation contains an amount of thermally insulative inorganicparticles in the range of from as low as about 10% up to as high asabout 60%, by weight of the layer of nonwoven fibrous thermalinsulation.
 4. The thermal runaway barrier according to claim 1, whereinthe layer of nonwoven fibrous thermal insulation contains an amount oforganic binder in the range of from as low as about 2.5% up to as highas about 10.0%, by weight of the layer of nonwoven fibrous thermalinsulation.
 5. The thermal runaway barrier according to claim 1, whereinthe layer of nonwoven fibrous thermal insulation has an installedthickness in the range of from about 0.5 mm up to less than 5.0 mm. 6.The thermal runaway barrier according to claim 1, wherein the layer ofnonwoven fibrous thermal insulation has a basis weight in the range offrom as low as about 250 g/m² and up to as high as about 1000 g/m². 7.The thermal runaway barrier according to claim 1, wherein the layer ofnonwoven fibrous thermal insulation has an uncompressed basis weight inthe range of from about 250 g/m² up to about 400 g/m².
 8. The thermalrunaway barrier according to claim 1, wherein the thermally insulativeinorganic particles further comprise particles of one or any combinationof the materials selected from the group consisting of inorganicaerogel, xerogel, hollow or porous ceramic microspheres, unexpandedvermiculite, fumed silica, otherwise porous silica, unexpanded perlite,pumicite, diatomaceous earth, titania and zirconia.
 9. The thermalrunaway barrier according to claim 1, wherein the layer of nonwovenfibrous thermal insulation is encapsulated by the organic encapsulationlayer.
 10. The thermal runaway barrier according to claim 9, wherein theorganic encapsulation layer has at least one vent hole formedtherethrough that is located and sized to allow gas contained within thethermal runaway barrier to escape from the organic encapsulation, suchthat the structural integrity of the organic encapsulation layer is keptintact, during a thermal runaway event.
 11. The thermal runaway barrieraccording to claim 9, wherein the thermal runaway barrier has a topedge, a bottom edge and opposite side edges, and the at least one venthole is located along the periphery of one or both opposite side edges.12. The thermal runaway barrier according to claim 9, wherein the atleast one vent hole provides an exit opening through the organicencapsulation layer having an opening area in the range of from about 2mm² up to about 15 mm².
 13. The thermal runaway barrier according toclaim 9, wherein the layer of nonwoven fibrous thermal insulation has aperipheral edge, and the organic encapsulation layer is sealed aroundthe peripheral edge.
 14. The thermal runaway barrier according to claim1, wherein the layer of nonwoven fibrous thermal insulation passes atleast the V-2 level of the UL94 Flammability Test.
 15. The thermalrunaway barrier according to claim 1, wherein the thermally insulativeinorganic particles comprise particles of irreversibly or permanentlyexpanded intumescent material.
 16. The thermal runaway barrier accordingto claim 1, wherein the thermally insulative inorganic particlescomprise particles of irreversibly or permanently expanded vermiculite.17. The thermal runaway barrier according to claim 16, wherein theexpanded vermiculite has been irreversibly or permanently expanded inthe range of from at least about 10% up to 100% of its expandability.18. A battery cell module for an electric vehicle, said battery cellmodule comprising: a plurality of battery cells disposed in a housing;and a plurality of thermal runaway barriers according to claim 1,wherein the battery cells are lined up in a row, with one thermalrunaway barrier being disposed between each pair of adjacent batterycells.
 19. A method of making the thermal runaway barrier according toclaim 1, wherein said method comprises: forming the layer of nonwovenfibrous thermal insulation using a wet-laid process or dry-laid process:providing thermally insulative inorganic particles that compriseunexpanded intumescent particles; disposing the thermally insulativeinorganic particles so as to be distributed within the layer of nonwovenfibrous thermal insulation; and heating the unexpanded intumescentparticles to a temperature and for a time that causes the unexpandedintumescent particles to irreversibly or permanently expand, whereinsaid heating occurs before or after the thermally insulative inorganicparticles are disposed within the layer of nonwoven fibrous thermalinsulation.
 20. The method according to claim 19, wherein said heatingoccurs after the unexpanded intumescent particles are disposed withinthe layer of nonwoven fibrous thermal insulation.